Water dispersible thermoplastic materials currently available generally comprise sulfonated polymers (see U.S. Pat. Nos. 3,734,874, 3,546,180 and 4,304,901). Sulfonation increases the degree of ionic character of a polymer and thus the water solubility, but leaves the polymer brittle. Extrusion of sulfonated polymers is possible, however, the resulting threadline cannot withstand winding.
The present invention overcomes problems of water dispersible polymers of the art by providing a polymer that is both water soluble and sufficiently flexible to permit winding.